Reply by Bob #2

Sawdust:If you visit a vacuum store that sells central vacs for houses they can show you their contact switch plates and probably offer you a wiring diagram. Bascially the gates are just wired in series so that any one contact that is closed will make a circuit to the relay. The relay will close and turn on the appliance.(DC)It’s harder to explain than to make one. They will probably have micro switches too and or you can buy gates preassembled and just run bell wire to each gate and to the relay. The relay will have a step down transformer like the one used for your door bell to drop the line voltage from 110 volts to 24 or 12 volts.I have built several over the years and have wired several Dental office with these systems for auto switching of theri suction systems.